Motor drives are power conversion systems or “converters” that operate to provide power to electric motors in a controlled fashion to control one or more motor performance parameters, such as speed, torque, etc. Medium voltage current-source type motor drives typically receive multiphase AC input power in the voltage range of about 2,400 to 6,900 volts, which is converted in a rectifier to DC power supplied to a DC link and provided from the DC link to an inverter. The inverter switches the DC link currents to provide AC output current to a motor load with the output current being controlled by the inverter in closed loop fashion to drive the motor at a desired speed and/or torque. The rectifier is generally an active switching type rectifier that selectively activates switches to provide current from the AC input to the DC link bus to achieve AC to DC power conversion, where the rectifier gain is controlled to provide a DC link current level at the peak current level required by the motor at any given time. The inverter, in turn, implements a switching scheme to selectively connect the motor leads to the DC link bus terminals to provide motor phase currents with controlled amplitudes, phase, and frequency to implement a particular motor control strategy based on motor performance feedback values and desired performance setpoints or profiles. Voltage source drives are similar but the DC link supplies a select constant DC voltage instead of a select constant DC current.
These motor drives generate large amounts of heat that must be exhausted from the various component housings/enclosures, e.g., from the common mode choke (CMC) housings/enclosures. This has previously been accomplished with redundant exhaust fan systems with two or more vertically stacked fans in which failure of one of the fans results in operation a redundant fan. These stacked fan systems are not suitable for use in applications where vertical space/height is limited. Also, the vertically stacked fans have been found to be suboptimal for other reasons such as noise, efficiency, and other reasons.